Best Practices - Exception Handling in C# .NET

Abstract

This article talks about best practices of exception handling, and guides you for some common programming mistakes developers do, as that seems appropriate in most applications written.

Best practices are only guidelines and do not enforce you to follow these, but if followed correctly then you won't only write less lines of code, but you work and code with more logical approach of coding and designing the code modules.

#1 Do Not Throw Exceptions to Control Application Flow

Scenario

The following code throws an exception inappropriately, when a supplied product is not found.

public static void CheckProductExists(int ProductId)
{
//... search for Product
if (ProductId == 0) // no record found throw error
{
throw (new Exception("Product is Not found in inventory"));
}
else
{
Console.WriteLine("Product is available");
}
}

static void Main(string[] args)
{
Console.WriteLine("Enter a ProductId you would like to search [1 – 100]");
int productId = Int32.Parse(Console.ReadLine());

CheckProductExists(productId);
Console.ReadLine();
}

After execution of Main, and when 0 is passed as shown in Figure 1-1 below.


Figure 1-1 Reading productId from Console

The value being passed to the program as shown in Figure 1-1 will result in an exception as shown in Figure 1-2 below.


Figure 1-2 Throwing exception when ProductId is 0 (Zero)

Problem

Throwing an exception as shown in Scenario section and Figures 1-1 and 1-2 is expensive; presumably throwing an exception causes the CPU to fetch code and data it would otherwise not have executed. You probably should not throw any exceptions in that scenario.

Solution

Consider the possibility that the code shown above not finding a product is an expected condition. Hence, re-factor the code to return a value that indicates the search result after the method's execution. The following code re-writes the code to verify the availability of the product in inventory and sets a flag to true or false.

This apparently avoids a new exception being thrown. The calling code uses a flag value to identify whether the inventory has the specified product or not.

public static bool CheckProductExists(int productId)
{
//... search for Product
if (productId == 0) // no record found
{
return false;
}
else
{
return true;
}
}

static void Main(string[] args)
{
Console.Write("Enter a ProductId you would like to search [1 – 100] : ");
int productId = Int32.Parse(Console.ReadLine());

if (!CheckProductExists(productId) == false)
{
Console.WriteLine("Found");

}
else

{